Embodiments of the present invention relate to organic colouring agents with a high colour stability to weathering for thermoplastics.
Embodiments of the invention furthermore relate to a polymer composition containing at least one thermoplastic and at least one organic colouring agent, preferably a combination of at least two organic colouring agents, of a specific structure.
Embodiments of the invention furthermore relate to the use of the colouring agents according to the invention for colouring polymer compositions, in particular for transparent formulations such as are required for the production of panes for use in buildings, motor vehicles and track vehicles or aircraft.
Embodiments of the present invention moreover relate to a process for the preparation of thermoplastic polymer compositions containing the colouring agent according to the invention or the colouring agent combination according to the invention.
Embodiments of the present invention furthermore provides the products, shaped articles or shaped objects produced from the thermoplastic polymer compositions coloured according to the invention.
The colouring of plastics is known per se.
Nevertheless, there has hitherto been a lack of colouring agent combinations, in particular for transparent formulations, which render possible a neutral colour formulation—e.g. a grey colour—and have an excellent stability to weathering for uses with high optical requirements. Uses with correspondingly high requirements of the colouring agent combinations used include, inter alia, transparent ready-made parts for automobile glazing which can be coloured to a varying degree depending on the use. Because of the long life of motor vehicles, in this context it is important in particular in the field of expensive automobiles for the desired high quality colour impression of the material to be retained without noticeable losses over the period of the useful life.
Glazing produced from compositions containing transparent thermoplastic polymers, such as e.g. polycarbonate, offers many advantages over conventional glazing of glass for use in the vehicle sector and for buildings. These include e.g. increased fracture-proof properties and/or saving in weight, which in the case of automobile glazing renders possible a higher safety of passengers in the event of traffic accidents and a lower fuel consumption. Finally, transparent materials which contain transparent thermoplastic polymers allow a considerably greater freedom of design due to the simpler formability.
Panes which are employed in the motor vehicle, track vehicle and aircraft or in the infrastructure sector must furthermore have a long life and should not become brittle during this life. The colour and transparency should moreover not change or change only slightly over the life, as is the case also for the IR protection properties with an appropriate IR protection finish of the panes, i.e. protection from thermal radiation. The pane must furthermore have an adequate scratch resistance.
Because of the long life required, glass is often employed as the glazing material. Glass is insensitive to UV radiation, has a low susceptibility to scratching and does not change its mechanical properties over long periods of time. Since inorganic oxides, such as e.g. iron oxide, are employed as pigments and IR absorbers, the IR and colour properties also remain practically unchanged over long periods of time. Nevertheless, the use of these pigments in thermoplastic materials is not possible, since it leads to clouding and/or degradation of the corresponding matrix.
On the basis of the advantages described above for plastics, there is therefore the need for materials which have both the good physical properties of thermoplastics and the high colour stability of correspondingly coloured glasses.
Among the transparent thermoplastics, polymers based on polycarbonate and polymethyl methacrylate (PMMA), for example, are particularly suitable for use as glazing material. Due to the high toughness, polycarbonate in particular has a very good profile of properties for such intended uses.
In order to improve the longevity of thermoplastic materials, it is known to provide these with UV protection and/or scratch-resistant coatings. A large number of colouring agents which have a high fastness to light are moreover known.
It has been found, nevertheless, that the thermoplastic compositions mentioned in the prior art are only inadequately suitable if an exceptionally high colour stability is required. This is the case e.g. if glass panes and transparently coloured panes of thermoplastic material are used together in construction. It is found here that the colour stability of glass is superior to that of the thermoplastic material. Colour deviations are striking in particular if these materials are used side by side in construction.
Bleaching out of colouring agents not only leads to the change in the colour properties, but also leads to a higher energy transmission occurring, since about 50% of the energy transmitted through a pane originates from the visual range of the solar spectrum. The latter is undesirable especially in the field of automobile and building glazing, since the particular inside temperature is thereby influenced.
It may furthermore be necessary to configure the colouring of the shaped article in a neutral colour, since the atmosphere of the interior or of the interior furnishings is influenced by an intensely coloured pane. As a rule, a grey of neutral colour is preferred. In certain embodiments, the colouring can be changed towards a blue-grey, a green-grey, red-grey or yellow-grey.
The composition must be processable under the conventional temperatures for thermoplastics, without the colour or other optical properties changing significantly during processing.
Many dyestuffs have been described as particularly fast to light and therefore also as stable in the prior art. The fastness to light (determined at ⅓ standard depth with 1% TiO2 (for Polystyrol 2% TiO2 in accordance with DIN EN ISO 4892-2; transparent dyeings with 0.05% of dyestuff; evaluated according to an 8-level blue scale) of the so-called Macrolex dyestuffs (Lanxess Data Sheets, Technical Information, Lanxess Deutschland GmbH, Functional Chemicals, High Performance Additives, Colorants, 51369 Leverkusen, Germany), such as e.g. the dyestuffs Macrolex® Blue RR (Solvent Blue 97), Macrolex® Violet 3R (Solvent Violet 36), which are envisaged for use in polycarbonate, has been classified with 7-8 (8=maximum value). Nevertheless, it was found in the context of the present experiments that colouring agents formally classified as fast to light do not have the stability according to the invention during weathering in polycarbonate compositions.
Rather, it has been found that only a very small number of colouring agents of a specific structure are suitable. In particular, specific combinations are suitable for achieving the present object.
There was therefore the object of providing colouring agents or a colouring agent combination with a high colour stability to weathering for thermoplastic polymers. In this context, the visual colour impression of the coloured thermoplastic polymer composition should change only slightly over life.
It was moreover an object of the present invention here to meet the following prerequisites in the case of transparently coloured thermoplastic polymer compositions:
The change in the colour values ΔE after 3,000 h of artificial weathering with exposure to xenon light at 0.75 W should be less than 5.0, preferably less than 4.0, particularly preferably less than 3.0. Furthermore, the visual colour impression, which means in particular streaks and points of high colour concentrations, also should not change.
In a particular embodiment, a neutral grey colour with colour values of a*=0±5 and b*=0+5, in particular a*=0±4 and b*=0÷4 is preferred.
In the context of the present invention, transparency is understood as meaning that the background when viewed through the transparent material, e.g. in the form of a corresponding shaped article, can be clearly detected. Mere transparency to light, such as e.g. in the case of frosted glass, through which the background appears only blurred, is not sufficient to describe the corresponding material as transparent. Transparent thermoplastic polymers or the thermoplastic polymer compositions in the context of the present invention furthermore have an initial clouding before weathering of less than 5.0%, preferably 4.0%, more preferably less than 3.0%, particularly preferably less than 2.0%.
A further object of the present invention was to provide a process for the preparation of thermoplastic polymer compositions containing the organic colouring agents according to the invention or the organic colouring agent combination.
It was furthermore the object of the present invention to provide coloured thermoplastic polymer compositions containing at least one organic colouring agent or one organic colouring agent combination for the production of multi-layer articles, mouldings and ready-made parts.
Surprisingly, it has been possible to achieve objects of the invention by the organic colouring agents according to the invention or the organic colouring agent combinations according to the invention and the thermoplastic polymer compositions according to the invention prepared using the organic colouring agents according to the invention or the organic colouring agent combinations according to the invention.